Rapid prototyping (RP) is a technology in which a part can be built layer by layer to a desired geometry, typically based on the instructions of a computer program, such as computer-aided design (CAD). Using RP, complex parts can be built with great precision and in short timeframes. In particular, a leading RP technique known as “fused filament fabrication” (FFF) can produce detailed and complex structures by its layer-by-layer process in which a fibrous material is extruded through a nozzle and deposited in a raster pattern (i.e., a pattern composed of parallel lines) in each layer. There has been significant interest in the use of these additive technologies to advance the manufacturing industry.
However, because only a limited number of materials, such as a limited number of thermoplastics and some engineering plastics, have been used as a feedstock for FFF, the final products generally have limited mechanical properties. In an effort to improve the mechanical properties, the conventional art has included reinforcing particles (i.e., fillers) with the polymer. The conventional means in the art for incorporating such filler material into a polymer matrix is by high shear mixing or compounding processes, typically provided by a screw extruder device, which is commonly either a single or twin screw extruder. However, a significant problem encountered with the high shear mixing processes of the art, particularly for filamentous particles, is filament breakage, which may occur by, for example, direct contact of the filaments with the screw and by filament-filament grinding. As the resulting filament breakage significantly undermines the original purpose of including the filament (i.e., improving tensile strength), current efforts in the conventional art for improving tensile strength and other characteristics of importance to rapid prototyping remain deficient.